The present invention relates to a starting fuel supply system for an internal combustion engine, comprising an electronic injection system, in particular, a sequential, timed electronic injection system.
Electronic injection systems on internal combustion engines are known to present an electronic control system which, depending on the signals received from various sensors (mainly engine speed/stroke and intake air pressure/temperature sensors), determines, for example, air density inside the manifold and engine speed, and calculates, via interpolation on respective memorised maps, the stroke and timing for injecting fuel into the injectors, as well as the spark lead. Such a sequential, timed electronic injection system therefore employs a given number of angular references on the drive and distributor shafts, for enabling the control system to determine the stroke (induction, compression, expansion, exhaust) of each cylinder. Each half revolution of the engine, the control system is therefore able to open the specific injector relative to the cylinder performing the required stroke. The engine strokes, however, must be identified by the control system within the shortest possible time after starting, for enabling correct fuel supply as soon as the engine is started up.
For fuel to be supplied correctly, i;e. full intake by the cylinder during the induction stroke, the exact stroke of each cylinder must be accurately determined for ensuring supply to the first cylinder in a position to complete a full induction and compression stroke. Such supply precision, however, conflicts with the need for the control system to supply the engine quickly and efficiently under unfavourable and, at times, even critical starting condittions. In fact, with the engine set at the worst possible starting angle, full identification of the engine strokes may mean waiting for the engine to turn through 820.degree., i.e. over two revolutions, before the first effective explosion is produced.